Abstract
•Novel Schiff’s base complexes were synthesized.•The complexes are characterized by different spectroscopic techniques.•Structure and spectra for the ligand and its metal (II/III) complexes were computed at the B3LYP/6-31G(d).•Ligand and its metal (II) complexes showed variable antimicrobial activities.
The Schiff’s base derived from condensation of s-triazole (4-amino-5-mercapto-3-methyl-S-triazole) with pyridine-2-aldehyde and their corresponding Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized. The isolated solid complexes were characterized by elemental analyses, molar conductance, spectral (IR, UV–Vis, 1H NMR, mass), magnetic moment and thermal measurements. The IR spectral data suggest that the ligand coordinate in a tridentate manner (SNN) via the one thiol (SH), one pyridine ring and the azomethine (CN) groups. The data show that the complexes have composition of ML2 type. The activation of thermodynamic parameters are calculated using Coats–Redfern, Horowitz–Metzger (HM), and Piloyan–Novikova (PN). The octahedral geometry of the complexes is confirmed using DFT method from DMOL3 calculations and ligand field parameters. Protonation constants of Schiff base and stability constants of their binary metal complexes have been determined potentiometrically in 50% DMSO–water media at 25°C and ionic strength 0.10M potassium nitrate. The biological activity of these compounds against various fungi has been investigated.